My first two attempts at entry to the US on my H1-B were simple, maybe one question and in I go. It was the third entry that they asked more questions and asked

My first two attempts at entry to the US on my H1-B were simple, maybe one question and in I go. It was the third entry that they asked more questions and asked to see more paperwork (which I did have with me). I guess it's to catch people who obtain visa/green-cards and then pass them off to others or their situation changes (and they no longer qualify for the visa). I'd also guess that frequent visitors to the US go through at least one of these increased scrutiny experiences every few years. I don't think it's unreasonable given the amount of problems they have with people trying to sneak into the country; I know that I don't have a right to be there so I expect some hassle. The only other problem I had was coming back into the US after I'd gone to Canada for a friend's wedding (all on a VWP); so UK->US, then two weeks later US->Canada->US, and I wasn't due to fly back to the UK for another 2 weeks or so. I was nowhere near the 90 days of my original VWP, but they might have thought I was taking a quick trip to Canada in order to reset my 90 days with a new VWP entry. It just took a few extra minutes explanation. Other than that I've done lots of trips to the US (20 on the Visa Waiver Program, 5 with my H1-B and another 10 or so since I moved back to the UK) with no problems at all.